Miasma Release is an advanced nature Kekkei Genkai which combines together the two elements Wind Release and Yin Release, and is from an unknown clan. The only time it's been used so far was by a cloaked man, and his identity has yet to be revealed, meaning the technique currently has unknown origins.
This Kekkei Genkai allows the user to spray a deadly, poisonous, purple wind, known as Miasma, out of their mouths. It's one of the deadliest poisons, capable of killing many enemies fairly quickly. It's extremely useful in large crowds. It's theorized that skilled users may even be able to transform the prexisting air or wind into the Miasma as well, although this has yet to be proven. Although a skilled Wind Release user can disperse the Miasma, if the Miasma user is more skilled at it than the opponent is at wind then it won't make that much of a difference at all.